Substrate treatment method and substrate treatment apparatus

ABSTRACT

In accordance with an embodiment, a substrate treatment method includes bringing a first metallic film on a substrate into contact with a first liquid, mixing a second liquid into the first liquid, and bringing the first metallic film or a second metallic film different from the first metallic film into contact with a liquid in which the first liquid and the second liquid are mixed together to etch the first or second metallic film. The first liquid includes an oxidizing agent, a complexing agent, and water (H2O) of a first content rate to etch the first metallic film. The second liquid includes water (H2O) at a second content rate higher than the first content rate after the etching has started.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/989,241, filed Jan. 6, 2016, which is based upon and claims thebenefit of priority from the prior Japanese Patent Application No.2015-111556, filed on Jun. 1, 2015, the entire contents of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to a substrate treatmentmethod and a substrate treatment apparatus.

BACKGROUND

A mixed chemical (mixed acid) including a phosphoric acid and a nitricacid may be used in a process of removing (etching) a metallic filmformed on a surface of a substrate such as a semiconductor wafer(hereinafter briefly referred to as a “wafer”).

Recently, in response to higher integration in semiconductor devices,development has been shifted to a new device in which a stack filmformed on a wafer is three-dimensionally processed from a conventionaldevice having a two-dimensional planar structure. In such a device, theuse of a process with the mixed acid is considered for the wet etchingof the metallic film of the stack film.

However, films slightly insoluble in acids such as a metallic filmincluding tungsten have the problem of the deterioration of etchingcharacteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing the overview of a substrate treatmentmethod according to one embodiment;

FIG. 2 is a graph showing an example of the change in the etching ratewith the passing of time according to the substrate treatment methodshown in FIG. 1;

FIG. 3 is a diagram showing the schematic configuration of a substratetreatment apparatus according to Embodiment 1; and

FIG. 4 is a diagram showing the schematic configuration of a substratetreatment apparatus according to Embodiment 2.

DETAILED DESCRIPTION

In accordance with an embodiment, a substrate treatment method includesbringing a first metallic film on a substrate into contact with a firstliquid, mixing a second liquid into the first liquid, and bringing thefirst metallic film or a second metallic film different from the firstmetallic film into contact with a liquid in which the first liquid andthe second liquid are mixed together to etch the first or secondmetallic film. The first liquid includes an oxidizing agent, acomplexing agent, and water (H₂O) of a first content rate to etch thefirst metallic film. The second liquid includes water (H₂O) at a secondcontent rate higher than the first content rate after the etching hasstarted.

Embodiments will now be explained with reference to the accompanyingdrawings.

A tungsten film is shown below as an example of a metallic film, andetching of this tungsten film is described by way of example. It shouldbe understood that the metallic film is not limited to the tungstenfilm, and, for example, an aluminum (AL) film or a titanium nitride(TiN) film is also applicable.

In addition, like components are provided with like reference signsthroughout the drawings and repeated descriptions thereof areappropriately omitted. Moreover, it is to be noted that the accompanyingdrawings illustrate the invention and assist in the understanding of theillustration and that the shapes, dimensions, and ratios and so on ineach of the drawings may be different in some parts from those in anactual apparatus.

First, a manufacturing method of a semiconductor device according to oneembodiment is described. FIG. 1 is a flowchart showing the schematicprocess of the manufacturing method of the semiconductor deviceaccording to the present embodiment.

As shown in FIG. 1, a mixed solution (hereinafter referred to as a“mixed acid”) including an oxidizing agent, a complexing agent, and abuffer is first prepared (step S1).

The oxidizing agent includes, for example, at least one of a nitric acid(HNO₃), hydrogen peroxide water (H₂O₂), and ozone (O₃). In the presentembodiment, the nitric acid (HNO₃) is used to oxidize a metal of ametallic film to be etched and then generate an oxide, and dissolve partof the metallic film into the mixed acid.

For example, a phosphoric acid (H₃PO₄) is selected as the complexingagent, and thereby complexes the metal oxide of the metallic film anddissolves the metal oxide into the mixed acid as a complex ion. Anacetic acid (CH₃COOH) is selected as the buffer in the presentembodiment, and thereby inhibits the generation of a nitric acidby-product, and preferentially volatilizes to inhibit the volatilizationof the nitric acid and the phosphoric acid.

The mixed acid includes pure water (H₂O). The mixed acid is prepared ina chemical bath (see the sign 12 in FIG. 3), for example, in the case ofan immersion type substrate treatment apparatus, or prepared in achemical tank (see the sign 24 in FIG. 4) coupled to an etchingtreatment portion (see the sign 22 in FIG. 4), for example, in the caseof a single-wafer type substrate treatment apparatus. In the presentembodiment, the mixed acid before etching corresponds to, for example, afirst liquid.

The mixed acid is then heated and kept at a predetermined temperature ormore (step S2). This process is required when the treatment target isthe slightly soluble metallic film. In the present embodiment, thetungsten film is targeted for a treatment, so that a temperature of 80°or more is maintained.

The mixed acid heated to 80° or more is then supplied to the treatmenttarget metallic film, and the metallic film is thereby etched (step S3).The oxidizing agent generates a metal oxide in the mixed acid, and thephosphoric acid of the complexing agent forms the metal oxide into acomplex ion and dissolves the complex ion into the mixed acid.

Components of the mixed acid change along with the etching. Morespecifically, the ratio of pure water contained in the mixed aciddecreases along with the etching. As a result, the etching ratedecreases by degrees. This is attributed to the fact that pure watervolatilizes earlier than the other mixed acid components because themixed acid during etching is at high temperature and that pure wateralso contributes to the reaction of complexing the metal oxide.

Therefore, even if the mixed acid having the same composition as that atthe start of the etching is added during the etching treatment, theratio of pure water contained in the mixed acid only slightly recovers,and the etching rate is not improved much.

Thus, pure water is added to the mixed acid during the etchingtreatment, specifically, before addition or after replacement of theoxidizing agent, the complexing agent, and the buffer (step S4). Thesubstance to be added is not exclusively pure water. It is possible touse a substance which has compositions similar to those of the mixedacid but in which the ratio of pure water is higher than the ratio ofpure water in the mixed acid used at the start of the etching. It isalso possible to use a mixed acid which has compositions different fromthe compositions of the mixed acid at the start of the etching but inwhich the ratio of pure water is higher than the ratio of pure water inthe mixed acid used at the start of the etching. In the presentembodiment, the substance added in step S4 corresponds to, for example,a second liquid. Moreover, in the present embodiment, the ratio of purewater in the mixed acid used at the start of the etching corresponds to,for example, a first content rate, and the ratio of pure water in thesubstance to be added corresponds to, for example, a second contentrate.

The timing of addition may be the time in which the etching treatmentfor the same treatment target is being conducted or may be the time inwhich the treatment target is replaced with another one. The amount ofpure water to be added is set to an amount suitable to the improvementof the etching rate in consideration of, for example, the amount of themixed acid at the start of the etching and the size and thickness of thetreatment target metallic film.

FIG. 2 is a graph showing an example of the change in the etching ratewith the passing of time according to the manufacturing method in thepresent embodiment. As shown in FIG. 2, it is apparent that the etchingrate gradually decreases along with the etching time but the etchingrate increases whenever pure water is added (see the sign C in FIG. 2),which enables stable etching. The decrease of the etching rate may bemonitored, and pure water may be added at the point where the etchingrate has become less than or equal to a predetermined value.Alternatively, pure water may be added at the point where apredetermined length of time has elapsed since the start of the etching.

According to the substrate treatment method in at least one embodimentdescribed above, pure water is added to the mixed acid during theetching treatment, so that the etching rate of the metallic film can bestabilized. Consequently, the metallic film can be stably etched withhigh controllability.

Next, etching apparatuses suitable to the implementation of theabove-mentioned substrate treatment method are described as substratetreatment apparatuses according to Embodiment 1 and Embodiment 2 withreference to FIG. 3 and FIG. 4.

An etching apparatus 10 shown in FIG. 3 is an example of an immersiontype substrate treatment apparatus, and includes a chemical bath 12, achemical tank 14, and a chemical addition line 16 provided between thechemical bath 12 and the chemical tank 14. The chemical tank 14 iscoupled to the chemical bath 12 by the chemical addition line 16.

The chemical bath 12 is coupled to an unshown heating circulationmechanism. For example, a mixed acid 1 kept at a high temperature of 80°or more is supplied to the chemical bath 12, and is retained in thechemical bath 12. A wafer W in which a treatment target metallic film MFis formed is immersed in the mixed acid 1 and etched. In the presentembodiment, the mixed acid 1 at the start of the etching corresponds to,for example, a first liquid, and the chemical bath 12 corresponds to,for example, a first container.

Pure water 2 is retained in the chemical tank 14. A predetermined amountof the pure water 2 is added to the chemical bath 12 via the chemicaladdition line 16 at a predetermined timing during the etching treatmentand then mixed into the mixed acid 1. In the present embodiment, thechemical tank 14 corresponds to, for example, a second container, thepure water 2 corresponds to, for example, a second liquid, and thechemical addition line 16 corresponds to, for example, a liquid supplypath.

According to the etching apparatus 10 shown in FIG. 3, the pure water inthe chemical tank 14 is added to and mixed into the mixed acid 1 in thechemical bath 12 during the etching treatment, so that the etching ratein the metallic film MF can be stabilized. Consequently, the metallicfilm MF can be stably etched with high controllability.

An etching apparatus 20 shown in FIG. 4 is an example of a single-wafertype substrate treatment apparatus, and includes the etching treatmentportion 22, the chemical tanks 24 and 26, and chemical addition lines 18and 28. The chemical addition line 28 is provided between the chemicaltank 24 and the chemical tank 26, and the chemical tank 26 is coupled tothe chemical tank 24 by the chemical addition line 28. The chemicaladdition line 18 is provided between the etching treatment portion 22and the chemical tank 24, and the chemical tank 24 is coupled to theetching treatment portion 22 by the chemical addition line 18.

The etching treatment portion 22 is provided with a holding table 22 aand a nozzle 22 b. The holding table 22 a holds the wafer W in which thetreatment target metallic film MF is formed. The nozzle 22 b has adischarge opening to discharge, to the wafer W, the mixed acid 1 comingfrom the chemical tank 24 via the chemical addition line 18.

The chemical tank 24 is coupled to an unshown heating circulationmechanism. The mixed acid 1 kept at a high temperature of, for example,80° or more is supplied to and retained in the chemical tank 24. Thepure water 2 is retained in the chemical tank 26. A predetermined amountof the pure water 2 is added to the chemical tank 24 from the chemicaltank 26 via the chemical addition line 28 at a predetermined timingduring the etching treatment, including a timing, for example, when thetreatment target wafer W is replaced.

In the present embodiment, the mixed acid 1 at the start of the etchingcorresponds to, for example, a first liquid, and the chemical tank 24corresponds to, for example, a first container. Moreover, in the presentembodiment, the pure water 2 corresponds to, for example, a secondliquid, the chemical tank 26 corresponds to, for example, a secondcontainer, the chemical addition line 28 corresponds to, for example, afirst liquid supply path, and the chemical addition line 18 correspondsto, for example, a second liquid supply path.

According to the etching apparatus 20 shown in FIG. 4, a predeterminedamount of pure water in the chemical tank 26 is mixed into the mixedacid 1 in the chemical tank 24 at a predetermined timing, so that themixed acid in which the amount of pure water has increased is dischargedto the wafer W from the nozzle 22 b. Thus, the etching rate in themetallic film MF on the wafer W can be stabilized. Consequently, themetallic film MF can be stably etched with high controllability.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The invention claimed is:
 1. A substrate treatment apparatus comprising:a chemical bath containing a first liquid comprising an oxidizing agent,a complexing agent, and water (H₂O), the water in the first liquid beingat a first content rate to etch a metallic film on a substrate immersedin the first liquid in the chemical bath; a chemical tank containing asecond liquid comprising the oxidizing agent, the complexing agent, andwater (H₂O), the water in the second liquid being at a second contentrate higher than the first content rate; and a liquid supply pathprovided between the chemical bath and the chemical tank to supply thesecond liquid in the chemical tank to the chemical bath to mix thesecond liquid with the first liquid in the chemical bath, wherein thechemical tank is configured to supply the second liquid to the chemicalbath at the point where an etching rate of the first liquid has becomeless than or equal to a predetermined value.
 2. The apparatus of claim1, wherein the chemical bath is configured to contain the substrate tobe etched.
 3. The apparatus of claim 1, wherein the oxidizing agentcomprises at least one of a nitric acid (HNO₃), hydrogen peroxide water(H₂O₂), and ozone (O₃).
 4. The apparatus of claim 1, wherein thecomplexing agent comprises a phosphoric acid (H₃PO₄).
 5. A substratetreatment apparatus comprising: a first chemical tank containing a firstliquid comprising an oxidizing agent, a complexing agent, and water(H₂O), the water in the first liquid being at a first content rate toetch a metallic film on a substrate; a second chemical tank containing asecond liquid comprising the oxidizing agent, the complexing agent, andwater (H₂O), the water in the second liquid being at a second contentrate higher than the first content rate; a first liquid supply pathprovided between the first and second chemical tanks to supply thesecond liquid in the second chemical tank to the first chemical tank tomix the second liquid with and the first liquid in the first chemicaltank; an etching chamber configured to contain the substrate to beetched; a second liquid supply path configured to supply the firstliquid or a liquid in which the first liquid and the second liquid aremixed together to the etching chamber from the first chemical tank; anda nozzle configured to supply the substrate with the first liquid or thefirst liquid mixed with the second liquid which has been suppliedthrough the second liquid supply path, wherein the second chemical tankis configured to supply the second liquid to the first chemical tank atthe point where an etching rate of the first liquid has become less thanor equal to a predetermined value.
 6. The apparatus of claim 5, whereinthe oxidizing agent comprises at least one of a nitric acid (HNO₃),hydrogen peroxide water (H₂O₂), and ozone (O₃).
 7. The apparatus ofclaim 5, wherein the complexing agent comprises a phosphoric acid(H₃PO₄).